Habitat+and+Ecosystem

=Habitat and Ecosystem=

Grizzly bears have their own specific habitat requirements. Grizzly bears use certain favorite plant and animal foods and will shift from one area to another in response to their seasonal abundance.

Early Spring - Late March / Early April - Out of the Dens
When grizzly bears come out of their dens in late March and April, food is localized and hard to come by. Some bears routinely travel to areas where they know there are carcasses of hoofed animals such as elk and moose. These areas include the winter range of these animals, railway tracks and roadsides, and the base of avalanche slopes where these animals may have been swept to their deaths. Other foods eaten by grizzly bears in early spring include the fresh shoots of grasses, the Hedysarum plant or "bear roots", and overwintered bearberries that have aged and have a high sugar content. All of these food sources occur in greatest abundance on steep south-facing slopes, usually at lower elevations.

**Late Spring - May and Early June**
A little later in the spring, during May and early June, grizzly bears concentrate their activities in river valley bottoms. Bears will eat lots of the tips of the primitive plant called horsetail which is high in crude protein. Horsetail is usually found in mature stands of spruce forest along streams and rivers. Hedysarum roots are excavated along the levees of braided stream channels of larger river systems. Bears continue to find big game carcasses in these habitats and, in some cases, they will even hunt for elk and moose calves.

Late June and July
In late June, in low-lying areas, horsetails and grasses have grown too fibrous to be nutritious. Grizzly bears start to seek out lush areas of vegetation that have developed more slowly. These areas include high elevation avalanche slopes, groundwater seepage areas, and smaller stream courses at upper elevations. Typical foods in these areas are horsetails, Cow Parsnip, Glacier lily, Spring Beauty, Valerian, and a variety of grasses. Hedysarum roots are eaten in mid-summer but not nearly as much as in the spring and fall. The larvae of ants and wasps are eaten wherever bears can find dried out logs and rocks to flip.

August Through Fall
Usually in early August, bears start to shift their diet to berries. At this time, some grizzly bears have been known to eat more than 200,000 berries in one day. On the drier east front of the Rocky Mountains, the buffaloberry is the main berry available. The most productive areas for buffaloberries are in open Lodgepole Pine forests in valley bottoms where soils are well drained and canopies are relatively open. In areas close to or west of the Continental Divide, grizzly bears eat blueberries and huckleberries during the months of August and September. These berries are prone to early fall frosts and bears are forced to switch to berries that stay on branches in spite of cold weather. These berries include Crowberry, Low bush Cranberry, and Mountain Ash. Ground squirrels are sought out in September when they are fat and slow. The diggings for ground squirrels are large and often trench-like. They reveal the large amount of effort that grizzly bears are willing to expend for this source of protein and minerals. During fall most grizzly bears supplement their berry diet with Hedysarum roots and even the nuts of Whitebark Pine trees.

Land Area Needed
Grizzly bears need a great deal of space to provide for their habitat needs. In order to access seasonally abundant and widely dispersed foods, grizzly bears must travel great distances. Grizzly bears that live in less productive habitat require much larger areas to feed in. The home range of grizzly bears in the eastern slopes of the Central Rockies Ecosystem is quite large, from about 500 sq. km for females to 1000 sq. km for males. Home range size in this region indicates that food sources are widely dispersed throughout the landscape rather than concentrated in local areas.

"Grizzly Bear Habitat." __Eastern Slopes Grizzly Bear Project__. 2008. Eastern Slopes Grizzly Bear Project. 31 July, 2008. 

=Historical Changes to the North American Grizzly Habitat= media type="googlemap" key="http://maps.google.com/maps/ms?hl=en&ie=UTF8&msa=0&msid=115226431057672449229.0004533668e2c08b4fd99&ll=48.077514,-116.191406&spn=52.268937,103.007812&output=embed&s=AARTsJruxVdinaDScih1s0vqpLR6dWAk-Q" width="425" height="350" Click [|here] for a Yellowstone Grizzly Fieldtrip in Google Earth (.kmz file)

This map created using [|resources] from [|Sightline Institute], a think tank, based in Seattle, WA. The map shows the changes in the North American Grizzly Bear Habitat over time. The yellow area on the map shows the estimated original range of the grizzly bear. The blue region shows the current range of the grizzly bear.